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Exploring the spectral information content in the LAMOST medium-resolution survey(MRS)

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Research in Astronomy and Astrophysics 2020年第4期20卷 57-68页

作者： Bo Zhang Chao Liu Chun-Qian Li Li-Cai Deng tai-sheng yan Jian-Rong Shi Key Laboratory of Optical Astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China

Although high-resolution stellar spectra allow us to derive precise stellar labels(effective temperature,metallicity,surface gravity,elemental abundances,etc.)based on resolved atomic lines and molecular bands,low-resolution spectra have been proved to be competitive in determining many stellar labels at comparable *** is useful to consider the spectral information content when assessing the capability of a stellar spectrum in deriving precise stellar *** this work,we quantify the information content brought by the LAMOST-II medium-resolution spectroscopic survey(MRS)using the gradient spectra as well as the coefficients-of-dependence(CODs).In general,the wavelength coverage of the MRS well constrains the stellar labels but the sensitivities of different stellar labels vary with spectral types and metallicity of the stars of ***,this affects the performance of the stellar label determination from the MRS *** applying the SLAM method to the synthetic spectra which mimic the MRS data,we find that the precision of the fundamental stellar parameters Teff,log g and[M/H]are better when combining both the blue and red bands of the *** is especially important for warm stars because the Hαline located in the red part plays a more important role in determining the effective temperature for warm *** blue and red parts together,we are able to reach similar performance to the low-resolution spectra except for warm ***,at[M/H]-2.0 dex,the uncertainties of fundamental stellar labels estimated from MRS are substantially larger than that from low-resolution *** also tested the uncertainties of Teff,log g and[M/H]from MRS data induced from the radial velocity mismatch and find that a mismatch of about 1 km s-1,which is typical for LAMOST MRS data,would not significantly affect the stellar label ***,reference precision limits are calculated using synthetic gradient spectra,according to which we expect a

关键词： methods:data analysis methods:statistical stars:fundamental parameters stars:abundances

Two New r-process-enhanced Stars with [Fe/H] >-0.6 dex from the LAMOST-MRS Survey

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Research in Astronomy and Astrophysics 2022年第7期22卷 109-117页

作者： Xiao-Jin Xie Jian-Rong Shi Tian-Lu Chen Hong-Liang yan Tian-Yi Chen Kai-Ke Pan Chun-Qian Li Shuai Liu Qi Gao tai-sheng yan Ming-Yi Ding Department of Physics College of ScienceTibet UniversityLhasa 850000China Key Laboratory of Optical Astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China Key Laboratory of Cosmic Rays(Tibet University) Ministry of EducationLhasa 850000China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China Apache Point Observatory SunspotNew Mexico 88349USA Astronomy Department New Mexico State UniversityLas CrucesNew Mexico 88003USA

We report the discovery of two r-process-enhanced stars with [Fe/H]>-0.6 dex selected from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST) *** candidate stars have been selected from the LAMOST medium-resolution(R~ 7500) spectroscopic survey,and the follo wed-up high signal-to-noise ratio and high-resolution(R~31,500) spectra are obtained with the ARC Echelle Spectrograph mounted on the3.5 m telescope at the Apache Point Observatory,which allow us for the determination of stellar atmospheric parameters and abundances of 20 *** these three r-process-enhanced candidate stars,TYC 1710-933-1 and TYC 2858-372-1 have [Eu/Fe] higher than 0.3 dex and [Ba/Eu] lower than 0.0 dex,thus,can be identified as new r-process-enhanced *** 2858-372-1 shows similar r+s-process pattern to the *** 1710-933-1 presents enhancement of the r-process elements of Nd and *** work indicates that the enrichment mechanisms of the heavy neutron-capture elements are complicated for metal-rich stars.

关键词： stars:abundances stars:chemically peculiar stars:fundamental parameters

Automatic modulation recognition of radio fuzes using a DR2D-based adaptive denoising method and textural feature extraction

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Defence Technology（防务技术） 2024年第4期34卷 328-338页

作者： yangtian Liu Xiaopeng yan Qiang Liu tai An Jian Dai Science and Technology on Electromechanical Dynamic Control Laboratory School of Mechatronical EngineeringBeijing Institute of TechnologyBeijing 100081China China Research and Development Academy of Machinery Equipment Beijing 100089China

The identification of intercepted radio fuze modulation types is a prerequisite for decision-making in interference ***,the electromagnetic environment of modern battlefields is complex,and the signal-to-noise ratio(SNR)of such environments is usually low,which makes it difficult to implement accurate recognition of radio *** solve the above problem,a radio fuze automatic modulation recognition(AMR)method for low-SNR environments is ***,an adaptive denoising algorithm based on data rearrangement and the two-dimensional(2D)fast Fourier transform(FFT)(DR2D)is used to reduce the noise of the intercepted radio fuze intermediate frequency(IF)***,the textural features of the denoised IF signal rearranged data matrix are extracted from the statistical indicator vectors of gray-level cooccurrence matrices(GLCMs),and support vector machines(SVMs)are used for *** DR2D-based adaptive denoising algorithm achieves an average correlation coefficient of more than 0.76 for ten fuze types under SNRs of-10 d B and above,which is higher than that of other typical *** trained SVM classification model achieves an average recognition accuracy of more than 96%on seven modulation types and recognition accuracies of more than 94%on each modulation type under SNRs of-12 d B and above,which represents a good AMR performance of radio fuzes under low SNRs.

关键词： Automatic modulation recognition Adaptive denoising Data rearrangement and the 2D FFT(DR2D) Radio fuze

Underdetermined direction of arrival estimation with nonuniform linear motion sampling based on a small unmanned aerial vehicle platform

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Defence Technology（防务技术） 2024年第3期33卷 352-363页

作者： Xinwei Wang Xiaopeng yan tai An Qile Chen Dingkun Huang Science and Technology on Electromechanical Dynamic Control Laboratory School of Mechatronical EngineeringBeijing Institute of TechnologyBeijing 100081China

Uniform linear array(ULA)radars are widely used in the collision-avoidance radar systems of small unmanned aerial vehicles(UAVs).In practice,a ULA's multi-target direction of arrival(DOA)estimation performance suffers from significant performance degradation owing to the limited number of physical *** improve the underdetermined DOA estimation performance of a ULA radar mounted on a small UAV platform,we propose a nonuniform linear motion sampling underdetermined DOA estimation *** the motion of the UAV platform,the echo signal is sampled at different ***,according to the concept of difference co-array,a virtual ULA with multiple array elements and a large aperture is synthesized to increase the degrees of freedom(DOFs).Through position analysis of the original and motion arrays,we propose a nonuniform linear motion sampling method based on ULA for determining the optimal *** the condition of no increase in the aperture of the physical array,the proposed method obtains a high DOF with fewer sampling runs and greatly improves the underdetermined DOA estimation performance of *** results of numerical simulations conducted herein verify the superior performance of the proposed method.

关键词： Unmanned aerial vehicle(UAV) Uniform linear array(ULA) Direction of arrival(DOA) Difference co-array Nonuniform linear motion sampling method

The Multiple Roles of Autophagy in Neural Function and Diseases

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Neuroscience Bulletin 2024年第3期40卷 363-382页

作者： yan-yan Li Zheng-Hong Qin Rui sheng Department of Pharmacology and Laboratory of Aging and Nervous Diseases Jiangsu Key laboratory of Neuropsychiatric DiseasesCollege of Pharmaceutical Sciences of Soochow UniversitySuzhou 215123China

Autophagy involves the sequestration and delivery of cytoplasmic materials to lysosomes,where proteins,lipids,and organelles are degraded and *** to the way the cytoplasmic components are engulfed,autophagy can be divided into macroautophagy,microautophagy,and chaperone-mediated ***,many studies have found that autophagy plays an important role in neurological diseases,including Alzheimer's disease,Parkinson's disease,Huntington's disease,neuronal excitotoxicity,and cerebral *** maintains cell homeostasis in the nervous system via degradation of misfolded proteins,elimination of damaged organelles,and regulation of apoptosis and ***-mTOR,Beclin 1,TP53,endoplasmic reticulum stress,and other signal pathways are involved in the regulation of autophagy and can be used as potential therapeutic targets for neurological ***,we discuss the role,functions,and signal pathways of autophagy in neurological diseases,which will shed light on the pathogenic mechanisms of neurological diseases and suggest novel targets for therapies.

关键词： Autophagy Neurodegenerative diseases Cerebral ischemia AMPK mTOR Beclin 1 TP53 Endoplasmic reticulum stress

De-biased knowledge distillation framework based on knowledge infusion and label de-biasing techniques

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Journal of Electronic Science and Technology 2024年第3期22卷 57-68页

作者： yan Li tai-Kang Tian Meng-Yu Zhuang Yu-Ting Sun School of Economics and Management University of Electronic Science and Technology of ChinaChengdu611731China School of Economics and Management Beijing University of Posts and TelecommunicationBeijing100876China School of Electrical Engineering and Computer Science The University of QueenslandBrisbane4072Australia

Knowledge distillation,as a pivotal technique in the field of model compression,has been widely applied across various ***,the problem of student model performance being limited due to inherent biases in the teacher model during the distillation process still *** address the inherent biases in knowledge distillation,we propose a de-biased knowledge distillation framework tailored for binary classification *** the pre-trained teacher model,biases in the soft labels are mitigated through knowledge infusion and label de-biasing *** on this,a de-biased distillation loss is introduced,allowing the de-biased labels to replace the soft labels as the fitting target for the student *** approach enables the student model to learn from the corrected model information,achieving high-performance deployment on lightweight student *** conducted on multiple real-world datasets demonstrate that deep learning models compressed under the de-biased knowledge distillation framework significantly outperform traditional response-based and feature-based knowledge distillation models across various evaluation metrics,highlighting the effectiveness and superiority of the de-biased knowledge distillation framework in model compression.

关键词： De-biasing Deep learning Knowledge distillation Model compression

Snowpack variations and their hazardous effects under climate warming in the central Tianshan Mountains

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Advances in Climate Change Research 2024年第3期15卷 442-451页

作者： Jian-sheng HAO yan WANG Lan-Hai LI Key Laboratory of Land Surface Pattern and Simulation Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of Sciences(CAS)Beijing 100101China Xinjiang Key Laboratory of Water Cycle and Utilization in Arid Zone Urumqi 830011China State Key Laboratory of Desert and Oasis Ecology Xinjiang Institute of Ecology and GeographyChinese Academy of SciencesUrumqi 830011China Tianshan Snowcover and Avalanche Observation and Research Station of Xinjiang Xinyuan 835800China CAS Research Center for Ecology and Environment of Central Asia Urumqi 830011China

Climate change alters snowpack evolution,which in turn influences the likelihood of snow avalanches and flood *** lack of systemic observational data on key snow characteristics in high mountains remains a scientific challenge in terms of systematically elucidating the dynamic chain of variations in climate-snowpack-snow *** restricts our understanding and poses challenges in the prediction of snow-related disaster *** such,this study analysed the variations of temperature and snowfall and the physical characteristics of snowpacks based on ground-based observations from the Kunse River Valley situated in the Tianshan Mountains from 1967 to *** results reveal that the temperature increased significantly by 0.32°C per decade(p<0.01)during the snow season,along with more extreme snowfall *** snow-cover duration was observed to have been shortened by 4.77 d per decade(p<0.01)from 1967 to 2021,which is characterised by later snow-cover onset and earlier ***,average and maximum snow depths increased along with an increase in peak snow water equivalent,thus indicating a higher frequency of extremely scarce or abundant snow *** low snowpack temperature gradient and earlier snowmelt dates in spring lead to earlier occurrences of snowmelt floods and wet *** the risks of these events increase,they pose greater threats to farmlands,road transportation,water-electricity infrastructure and several other human ***,these insights are critical for providing vital information that can deepen our understanding of the impact of climate change on snowpack characteristics and improve management strategies for snow-related disaster prevention and mitigation.

关键词： Climate change Snowpack variations Snow-related disaster Tianshan Mountains

A novel metal-free porous covalent organic polymer for efficient room-temperature photocatalytic CO2 reduction via dry-reforming of methane

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Green Energy & Environment 2024年第9期9卷 1407-1418页

作者： sheng-yan Yin Ziyi Li Yingcai Hu Xiao Luo Jishan Li College of Chemistry and Chemical Engineering Hunan University Institute of Basic Medicine and Cancer (IBMC) Chinese Academy of Sciences

At room temperature,the conversion of greenhouse gases into valuable chemicals using metal-free catalysts for dry reforming of methane（DRM） is quite promising and ***,we developed a novel covalent organic porous polymer （TPE-COP） with rapid charge separation of the electron–hole pairs for DRM driven by visible light at room temperature,which can efficiently generate syngas （CO and H2）.Both electron donor (tris（4-aminophenyl）amine,TAPA) and acceptor (4,4',4'',4'''-(（1 E,1'E,1''E,1'''E）-(ethene-1,1,2,2-tetrayltetrakis （benzene-4,1-diyl）)tetrakis （ethene-2,1-diyl）)tetrakis (1-（4-formylbenzyl）quinolin-1-ium),TPE-CHO) were existed in TPE-COP,in which the push–pull effect between them promoted the separation of photogenerated electron–hole,thus greatly improving the photocatalytic *** functional theory （DFT） simulation results show that TPE-COP can form charge-separating species under light irradiation,leading to electrons accumulation in TPE-CHO unit and holes in TAPA,and thus efficiently initiating *** 20 h illumination,the photocatalytic results show that the yields reach 1123.6 and 30.8μmol g-1for CO and H2,respectively,which are significantly higher than those of TPE-CHO small *** excellent result is mainly due to the increase of specific surface area,the enhancement of light absorption capacity,and the improvement of photoelectron-generating efficiency after the formation of ***,this work contributes to understanding the advantages of COP materials for photocatalysis and fundamentally pushes metal-free catalysts into the door of DRM field.

关键词： Metal-free Photocatalytic CO 2 reduction Covalent organic polymer Dry-reforming of methane Electron donor and acceptor

Engineering Ru（N^N）3-modified covalent organic framework for photocatalytic olefin epoxidation

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Science China Chemistry 2024年第11期67卷 3719-3728页

作者： yan-Lin Li sheng-Li Huang Guo-Yu yang Key Laboratory of Cluster Science (Ministry of Education) Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion MaterialsSchool of Chemistry and Chemical Engineering Beijing Institute of Technology

Photocatalytic olefin oxidation using air as an oxidant is an environmentally friendly method for producing epoxides. Covalent organic frameworks（COFs） have emerged as promising photocatalysts in various organic synthesis reactions. The combination of tri-（2-pyridinal aldehyde）-containing precursor with 4,4’,4’’-（1,3,5-triazine-2,4,6-triyl）trianiline generated（N^N）-I-COF. Via imine-to-quinoline transformation and coordination anchorage of Ru（N^N）3unit, Ru（N^N）3@Q-COF was obtained with improved chemical stability, skeleton conjugation, and novel photochemical characteristics, and demonstrated excellent photocatalytic activity in olefin epoxidation with a wide range of substrates. The presence of H2O played a crucial role in the formation of reactive oxygen species（ROSs）, which in turn influenced the olefin oxidation process. The hydrophilicity of Ru（N^N）3facilitated the approach of H2O and O2to the photogenerated charges, thereby promoting ROSs generation. The lipophilicity of Q-COF allowed for the absorption of olefin substrates, and its nano-channels increased encountering possibility between olefins and ROSs. Consequently, Ru（N^N）3@Q-COF provided an intriguing platform for olefin photooxidation and could be recycled multiple times without any degradation in performance. This report revealed that the conversion of classical ROSs into less potent oxidants with rapid kinetic rates played a crucial role in achieving highly efficient and selective epoxidation of terminal olefins.

关键词： polypyridyl Ru covalent organic framework olefin epoxidation photocatalysis